1. Field of the Invention
The present invention relates in general to subterranean wells, and in particular to a seal with an energizing ring and a retention assembly, for sealing between wellhead members.
2. Brief Description of Related Art
In hydrocarbon production wells, a housing such as a wellhead housing of high pressure housing is located at the upper end of the well. The wellhead housing is a large tubular member having an axial bore extending through it. Casing will extend into the well and will be cemented in place. A casing hanger, which is on the upper end of the casing, will land within the wellhead housing. The exterior of the casing hanger is spaced from the bore of the wellhead housing by an annular clearance which provides a pocket for receiving an annulus seal.
There are many types of annulus seals, including rubber, rubber combined with metal, and metal-to-metal. One metal-to-metal seal in use has a U-shape in cross section, having inner and outer walls or legs separated from each other by an annular clearance, called a seal pocket. An energizing ring, which has smooth inner and outer diameters, is pressed into the seal pocket to force the legs apart to seal in engagement with the bore and with the exterior of the casing hanger.
During operations, cyclic loads and pressures can cause the energizing ring to back away from the annulus seal, allowing the seal to leak. In metal-to-metal seals with U-shaped cross sections, the energizing ring can back out of the seal pocket. Previous assemblies have utilized a single bump feature where a relatively high setting load is required to force the energizing ring to energize the seal ring. A press is required to assemble such assemblies. The energizing ring of such assemblies must be forced within the seal ring until the single bump feature has been passed. If additional axial movement of the energizing ring into the seal ring is required to fully set the seal ring, after the bump feature has been passed, during operation, the energizing ring can back out of the seal ring until the bump feature restricts further axial movement of the energizing ring. This backing out of the energizing ring can cause the seal ring to leak.